How Kingda Ka Works: Demystifying the Launch System that Rockets the Coaster

When it debuted in 2005, Kingda Ka at New Jersey's Six Flags Great Adventure laid claim to the twin titles of the world's tallest and fastest roller coaster. Its 50.6-second adrenaline rush of a ride sends coaster freaks up a 456-foot top hat tower and reaches a maximum speed of 128 mph in 3.5 seconds. Yikes!

If that pithy explanation has you scratching your head, you're not alone.

To help get a better sense of what rockets hydraulic rocket coasters (similar thrill machines include Top Thrill Dragster at Cedar Point and Xcelerator at Knott's Berry Farm), I sat down with Michael Reitz, a corporate engineer with Six Flags and a member of the team that worked on Kingda Ka.

Up until the late 1970s, nearly all roller coasters were fairly standard. Whether the tracks were made of wood or steel, a poky lift chain, powered by a motor, click-clack-clicked coaster trains slowly up a lift hill. At the top of the hill, the chain disengaged and gravity took over.

Most new coasters still use the tried-and-true approach, but attraction designers have been experimenting with a number of launch systems to ratchet up the acceleration, speeds, heights, and (of course) the thrills, as well as create different kinds of ride experiences. Screaming out of the loading station, Kingda Ka and the new breed of coasters eliminate the anticipation of the lift hill and deliver non-stop action from beginning to end.

To send coaster trains -- and their fearless passengers -- screaming from the get-go, launch systems have used compressed air, magnetic propulsion, jazzed-up electric motors, and even a low-tech weight-drop system that sounds like something Rube Goldberg might have invented. But hydraulics offer a relatively simple and efficient way to quickly get coaster cars moving fast -- VERY fast.

A Coaster on Steroids

The concept of a hydraulic launch system is similar to a traditional lift-hill coaster...on mega doses of steroids. Instead of a lift chain, the coaster uses a cable that is wound around a giant winch. Attached to the cable is a catch car, a device that latches onto the trains and rockets them down the launch track. To marry the two, a "dog" drops down from the center of the train and hooks into the catch car. About two-thirds of the way down Kingda Ka's horizontal launch track, the train accelerates to its top speed, the dog lifts and disengages from the train, magnetic brakes slow the catch car, and the train continues up the 456 vertical top hat tower. Gravity takes the train down the other side of the tower and back to the station.

Unlike conventional coasters, which typically reach their highest speed after roaring down the first drop, Kingda Ka clocks in at 128 mph on the approach to the tower. "In theory, we'd want to hit the same speed on both sides of the tower," says Reitz. "But wind, the weight load of the passengers, heat, humidity, and other factors affect the actual speeds." He says that Kingda Ka usually revs up to about 120 mph at the bottom of the other side of the tower before it navigates its second hill and heads home.

That explains how Kingda Ka's trains tear out of the loading station. But how does the winch produce enough thrust to yank the cable down the launch track? Hydraulics.

OK, you can stop scratching your head now. Reitz explains that the winch is connected to eight 500-hp hydraulic motors that sit atop a huge reservoir of hydraulic fluid. Compressed nitrogen gas forces the fluid through the motors to generate energy. The engineer notes that the motors send the energy they create intro giant accumulators and likens the process to blowing up balloons.

"They store huge amounts of energy, then at the precise moment, poof, they release it," he says. "They are capable of producing 20,800 peak horsepower." For comparison, a car's engine usually delivers about 175 hp. We're talking some serious power here.

Even Faster and Taller?

With its ultra-high, ultra-fast specs, Kingda Ka begs the question: How much taller and faster could designers make coasters? "The challenge is not 'Can we do it?' " Reitz says, alluding to the ongoing coaster brinkmanship. "The question is 'At what cost?' "

Parks can count on coaster fans lining up to test their mettle on bigger, faster thrill machines, but bragging rights only go so far when bean counters look at the return on investment. The sky, apparently, is the limit (as is the speedometer), but how many parks would be willing to shell out the tens of millions of dollars it would cost to build coasters that pierce the sky?